Open tool molding is a process for producing relatively low cost composite panels at low volumes. While steel molds are often used for other molding operations, the open tool molding process was developed to use less expensive one-sided epoxy or polyester molds to produce various products, such as recreational vehicle (RV) composite panels with an in-mold finish. In this process, the mold surface is cleaned and waxed, after which a layer of gel coat is applied and then partially cured. A laminate is then applied to the gel coat layer, and the laminate and gel coat are cured to form a unitary part having a surface that is defined by the cured gel coat. Molded parts can be produced by this method to have a class A finish bearing any desired color originally carried by the gel coat.
While the use of a low-cost epoxy or polyester mold offers significant cost advantages over other molding methods used to produce composite articles, there are certain limitations imposed by a polymeric mold. One such example is the molding of panels, such as automotive interior panels, for which a textured finish, such as a leather grain look, is desired. Most typically in the past, plastic textured panels have been made by either injection molding or compression molding using steel molds. A grained profile is formed on the surface of the steel mold during the tool making process. The grained surface profile is then transferred onto the surface of the molded parts, creating a textured surface finish. Because of the hardness of the steel molds, the grained surfaces maintain their appearance for many years of production. In contrast, polymeric molds do not have the same level of hardness and, therefore, a grained surface created on a polymeric mold wears out quickly. The vertical walls of a grained polymeric mold are particularly vulnerable to wear during demolding, with the result that an uneven surface finish is produced after molding only a few parts. Consequently, polymeric open tool molds have been generally limited to molding articles with smooth, glossy surfaces.
Alternatively, the composite articles can be given a textured finish by a molding process that uses an interfacial layer to isolate the surface of the mold from the surface of a composite article produced with the mold. According to that approach, a solution can be sprayed on the mold surface to form the interfacial layer, whose surface opposite the mold surface is textured. The texture of the interfacial layer is then transferred to the surface of the composite article produced with the mold. After demolding, the interfacial layer is removed from the article to expose an underlying textured surface of the article. While this approach works well, it requires an additional spraying step for the interfacial layer and the textured surface of the sprayed interfacial layer must also be closely controlled to produce a high quality surface finish on the article. In addition, curing time is required for the interfacial layer to become sufficiently stable prior to the composite layer being applied. Such an example can be found in commonly-assigned U.S. Ser. No. 09/587,393 filed Jun. 5, 2000, entitled “Method of Forming a Composite Article with a Textured Surface”.
In view of the above, it would be desirable if a method were available for producing composite articles with a textured finish using a simplified approach that eliminates that need for the spraying and curing of an interfacial layer.